Vaccination Programs

– William P. Shulaw DVM MS, Extension Veterinarian, Beef/Sheep, The Ohio State University (excerpted from the OSU Extension Feedlot Management Primer)

Vaccines are commonly administered to calves entering a feeding program. However, the bovine respiratory disease complex (BRDC) is a perplexing syndrome that involves the interactions of a number of viruses, bacteria, and stress factors. The very number of different vaccination programs and vaccines available suggest that no one program, or possibly even any program, is highly satisfactory in preventing BRDC or shipping fever. Vaccines should be viewed as tools in our armamentarium for the prevention of BRDC, and it should be realized that they have limitations.

Vaccination programs for the feedlot should be developed between the producer and veterinarian and in consideration of farm goals, expected outcomes, and cost benefit. Some general points may be useful for consideration:

1. Vaccines are intended for use in stimulating an immune response in an animal that results in both a humoral (antibody and cytokine-mediated) and a cellular response that offers protection by preventing infection or neutralizing the factors that cause disease. This response is optimal only in a normal, reasonably healthy animal. An animal responding satisfactorily is said to be immunized. Vaccination does not equal immunization.

2. Time is needed for an adequate response to vaccines. Significant antibody levels may not be reached for 14 to 21 days in many cases and may only be reached following a booster dose in others.

3. The presence of maternal antibody (gained from the colostrum), which may persist up to 5-6 months-of-age, may interfere with the development of an adequate immune response.

4. Multiple strains of some viruses and bacteria exist in the field. Vaccines may not always be available which protect against all strains.

5. Live and killed vaccines are both available and each has distinct advantages and disadvantages. Modified live virus (MLV) vaccines tend to stimulate protection sooner than killed vaccines and may do so in a susceptible animal with one dose. MLV vaccines are generally cheaper than killed virus vaccines but require a normal immune system to work. Killed vaccines usually require at least 2 doses 3-4 weeks apart for optimal protection but are free from potential contaminants such as free live virus. Killed virus vaccines generally do not cause the immune suppression sometimes seen with live vaccines and are usually safe in pregnancy.

6. Poor vaccine handling techniques can cause live vaccines to die and be worthless, and any vaccine can become contaminated and dangerous to use.

7. The immune system of any animal can be impaired by lack of adequate energy, protein, and essential micronutrients such as Se, Cu, Zn, and vitamins C and E.

8. Vaccine efficacy – Not all available vaccines stimulate protective immunity.